Apparatus, and associated method, for facilitating communications by a mobile node in a multiple network radio communication system having interworking capability

ABSTRACT

Apparatus, and an associated method, by which to permit selection by a user of a mobile node of with which cellular communication system network that the mobile node shall communicate by way of an interworking wireless local area network. User selection is provided even when the interworking wireless local area network is directly connected to the home network of the mobile node. A determiner determines whether the interworking wireless local area network is directly connected to the home network. And, responsive to the determinations, an identifier identifies the cellular communication system network associated with the interworking wireless local area network.

This application is a continuation of U.S. application Ser. No.11/943,267, filed on Nov. 20, 2007, entitled, “Apparatus And AssociatedMethod For Facilitating Communications By A Mobile Node In A MultipleNetwork Radio Communication System Having Interworking Capability,”,which is a continuation of U.S. application Ser. No. 10/914,511, filedon Aug. 9, 2004, entitled, “Apparatus And Associated Method ForFacilitating Communications By A Mobile Node In A Multiple Network RadioCommunication System Having Interworking Capability.” The entirecontents of which are hereby expressly incorporated by reference hereinin their entireties.

The present invention relates generally to a manner by which tofacilitate communications by a mobile node with a selected PLMN (publicland mobile network) by way of a WLAN (wireless local area network)pursuant, e.g., to interworking between a 3GPP (Third GenerationPartnership Project) network and an I-WLAN (interworking-wireless localarea network). More particularly, the present invention relates toapparatus, and an associated method, by which to obtain information atthe mobile node of available PLMNs with which the mobile node is able tocommunicate, even when the WLAN is directly connected to an HPLMN thatis associated with the mobile node.

A determination is made whether a WLAN, with which the mobile node is incommunication connectivity, is directly connected to the HPLMN (homepublic land mobile network) of the mobile node. If so, the mobile nodecauses its authentication with the WLAN to fail, precipitating the WLANto send PLMN information to the mobile node that identifies the PLMNswith which the mobile node is able to communicate by way of the WLAN.Automatic communication by the mobile node with the HPLMN that wouldotherwise result, due to the direct connection of the WLAN with theHPLMN, is avoided. Instead, the user of the mobile node is able toselect with which of the available PLMNs with which the mobile nodeshall communicate.

BACKGROUND OF THE INVENTION

Modern communication systems have benefited from advancements incommunication technologies. When implemented in existing communicationsystems, such advancements provide for improved communications, e.g.,more efficient communication of data, communication of data at highercommunication rates, or in manners that better provide for thesuccessful communication of the data in adverse communicationconditions. And, advancements in communication technologies havepermitted the development of new types of communication systems,providing for the effectuation of new types of communication services.As advancements in communication technologies shall likely continue,their implementation into existing and yet other new communicationsystems shall likely also continue in the future.

Communication systems are regularly utilized by many, and, for manyusers, ready access to communicate by way of any of variouscommunication systems is necessary. Data is communicated upon acommunication system by a user both to send data to another location andto receive data that is sent from a remote location.

Advancements in digital communication technologies are amongst thetechnological advancements that have been implemented in communicationsystems. Use of digital communication techniques provides variouscommunication advantages. For instance, improved communicationefficiencies are provided as redundancies in data that is to becommunicated are removed prior to communication of the data. Byimproving the communication efficiency, the throughput rate of the datain the communication system is increased, relative to the throughputrate permitted of a corresponding analog communication system.

A radio communication system is an exemplary type of communicationsystem. In a radio communication system, communication stations operabletherein send and receive data communicated upon radio communicationchannels. The radio communication channels are defined upon portions ofthe electromagnetic spectrum. Free of the need to interconnectcommunication stations by way of wireline connections, radiocommunication systems permit for the effectuation of communicationsbetween locations at which interconnection of communication stations byway of wireline connections would not be possible or practical.Additionally, a radio communication system is implementable as a mobilecommunication system providing communication mobility to thecommunications.

A cellular communication system is an exemplary type of radiocommunication system. A cellular communication system includes a networkpart, referred to as network infrastructure, that is installed over ageographical area that is encompassed by the communication system.

Cellular communication systems generally conform to operationalparameters set forth in an operating specification. Operatingspecifications are promulgated by standard-setting, regulatory bodies.And, the regulatory bodies have promulgated successive generations ofoperating standards, each generation taking advantage of advancements incommunication technologies.

The network infrastructures of more than one generation of cellularcommunication system might well be installed to encompass commongeographical areas. And, the network infrastructures of cellularcommunication systems of the same generation, operated, e.g., bydifferent network operators, might also be installed over a commongeographical area.

Additionally, wireless local area networks (WLANs) have also beendeveloped and deployed. WLANs are also radio communication systems, andsuch systems are operable, at least in various aspects, in manners thatare analogous to operation of cellular communication systems. Wirelesslocal area networks are generally implemented as small-area systems thatencompass areas generally smaller than the areas encompassed by cellularcommunication systems.

Wireless local area networks, in some respects, are technologicalextensions of conventional local area networks. That is to say, bothconventional local area networks and wireless local area networksgenerally provide for the communication of packet-formatted data and aregenerally able to effectuate data-intensive packet communicationservices. The mobile nodes of the wireless local area network areanalogous to, and functionally equivalent to, the fixed nodes of theconventional local area network.

The communication protocols of a wireless local area network and acellular communication system are not necessarily the same, andfrequently are not, the same. Mobile nodes are sometimes constructed tobe operable in both a cellular communication system and a WLAN.

When a user of the mobile node effectuates communication of datapursuant to a communication service, selection must be made of a networkby way of which to communicate. Interworking between wireless local areanetworks and the networks of cellular communication systems is ongoingand operating protocol standards are undergoing development.

It is generally desired to permit the user of the mobile node, when incommunication connectivity with a particular wireless local areanetwork, to permit the mobile node to communicate with a cellularcommunication system network, if selected, and if so, further to permitthe user of the mobile node to select with which cellular communicationsystem network to communicate if more than one cellular communicationsystem network is associated with the wireless local area network. Theuser of the mobile node is provided with indications of the cellularcommunication system networks available with which to communicate by wayof the wireless local area network as a result of broadcasts of suchinformation by the wireless local area network. The information isprovided to the mobile node, e.g., pursuant to authenticationprocedures.

Existing procedures by which to provide the information to the user ofthe mobile node is susceptible to problems when the wireless local areanetwork with which the mobile node is in the communication connectivityis directly connected to a home public land and mobile network (HPLMN)of the mobile node, as communications between the mobile node and theHPLMN are automatically effectuated. The user of the mobile node is notprovided with the capability of selection of with which cellularcommunication system network that the mobile node shall communicate.

An improved manner by which to permit user selection even when thewireless local area network is directly connected to the HPLMN of themobile node is therefore required.

It is in light of this background information related to communicationof data in a multiple network communication system that the significantimprovements of the present invention have evolved.

SUMMARY OF THE INVENTION

The present invention, accordingly, advantageously provides apparatus,and an associated method, by which to facilitate communications by amobile node with a selected public land mobile network by way of awireless local area network, e.g., pursuant to interworking between a3GPP (Third Generation Partnership Project) network and an I-WLAN(interworking-wireless local area network).

Through operation of an embodiment of the present invention, a manner isprovided by which to obtain information at the mobile node of availablepublic land mobile networks with which the mobile node is able tocommunicate, even when the wireless local area network is directlyconnected to the home-public land mobile network associated with themobile node.

In one aspect of the present invention, a determination is made whethera wireless local area network, with which the mobile node is incommunication connectivity, is directly connected to the home publicland mobile network of the mobile node. If so, then the mobile nodecauses its authentication to fail, precipitating the wireless local areanetwork to send the public land mobile network information to the mobilenode. The information identifies the public land mobile networks withwhich the mobile node is able to communicate by way of the wirelesslocal area network.

Thereby, automatic communication by the mobile node with its home publicland mobile network that would otherwise result due to the directconnection of the wireless local area network with the home public landmobile network is avoided. The user is provided with the information ofthe public land mobile networks with which communications areeffectuable, and the user of the mobile node is able to make selectionof with which of the available networks that communications shall beeffectuated.

During operation of the mobile node, the mobile node searches for thewireless local area networks with which the mobile node is able tocommunicate. The search performed by the mobile node comprises, forinstance, scans of frequencies at which access points, or otherstructure, of wireless local area networks that broadcast signals thatidentify their presence. When the mobile node detects a wireless localarea network that is permitting of communication connectivity with themobile node, the mobile node commences procedures by which to permitcommunication between the mobile node and the selected wireless localarea network. The mobile node includes, for instance, a list thatidentifies preferred wireless local area networks with which thecommunications are preferred over networks not contained on the lists.

In one implementation, the mobile node also includes a list thatidentifies cellular communication system networks that are associatedwith wireless local area networks. When the mobile node detects wirelesslocal area networks with which the mobile node is able to enter intocommunication connectivity, the list is accessed to determine whether acellular communication system network associated therewith is a homenetwork associated with the mobile node. The list further indicateswhich of the cellular communication system networks are directlyconnected to the associated wireless local area network.

Responsive to access to the list, or otherwise, a determination is madeas to whether the selected wireless local area network is directlyconnected to the home network associated with the mobile node. If thewireless local area network is directly connected to the home network ofthe mobile node, the mobile node initiates an authentication procedurethat causes the mobile node to fail its authentication. Upon failure ofthe authentication, the wireless local area network provides a list tothe mobile node of the cellular communication system networks, i.e., thePLMNs, that are associated with the wireless local area network and withwhich the mobile node is able to communicate through its communicationconnection with the wireless local area network.

In the exemplary implementation, the mobile node performs authenticationprocedures with a root network address identifier (NAI) that is of avalue other than the value of the root network address identifier thatwould properly authenticate the mobile node. The other value is stored,for instance, at the mobile node, and the value is retrieved when adetermination is made that the selected wireless local area networkmaintains a direct connection with the home network associated with themobile node. By sending the root network address identifier of the othervalue, authentication fails. And, the wireless local area network,pursuant to the authentication failure, provides the mobile node withindications of which cellular communication system networks areaccessible by way of the wireless local area network. Thereby, a user ofthe mobile node is provided with indications of the available cellularcommunication system networks, permitting the user to make selection ofwith which of the cellular communication system networks that with whichcommunications shall be effectuated by way of the selected wirelesslocal area network.

In these and other aspects, therefore, apparatus, and an associatedmethod, is provided for a mobile node selectably operable to communicatein a multi-network communication system. The communication system has afirst set of first type networks and a second set of second typenetworks. The mobile node is associated with a home network comprises ofa second type network of the second set. Communication by the mobilenode, once connected in communication connectivity with a first typenetwork of the first set, with a selected network of the second set isfacilitated. A determiner is adapted to receive indications of a directconnection between the network of the first set with which the mobilenode is connected in the communication connectivity and the home networkassociated with the mobile node. The determiner determines if thenetwork of the first set with which the mobile node is connected in thecommunication connectivity is directly connected with the home network.An identifier is operable at least responsive to determination by thedeterminer of the direct connection between the first network and thehome network. The identifier identifies which, if any, of the networksof the second set of networks are available with which to communicatewith the mobile node.

A more complete appreciation of the present invention and the scopethereof can be obtained from the accompanying drawings that are brieflysummarized below, the following detailed description of thepresently-preferred embodiments of the present invention, and theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a functional block representation of a multiplenetwork communication system in which an embodiment of the presentinvention is operable.

FIGS. 2A and 2B illustrate representations of a listing maintained atthe mobile node that identifies wireless local area networks and whethersuch wireless local area networks maintain direct connections with ahome network associated with the mobile node.

FIG. 3 illustrates a message sequence diagram representative ofsignaling generated during exemplary operation of the communicationsystem shown in FIG. 1 pursuant to an embodiment of the presentinvention.

FIG. 4 illustrates a method flow diagram listing the method of operationof an embodiment of the present invention.

DETAILED DESCRIPTION

Referring first to FIG. 1, a communication system, shown generally at10, provides for radio communications with mobile nodes, which themobile node 12 is representative. The mobile node forms a dual-mode,mobile node capable of operation in a first manner and at least a secondmanner. In the exemplary implementation, the mobile node is separatelyoperable pursuant to an IEEE 802.11(b), or variant, operatingspecification, and a 3GPP (Third Generation Partnership Project)operating standard. In other implementations, the mobile node isoperable pursuant to other operating standards. Accordingly, while thefollowing description of exemplary operation of an embodiment of thepresent invention shall be described with respect to its implementationin which the data is communicated pursuant to the operating protocols ofthe IEEE 802.11(b) and 3GPP operating specifications, operation of anembodiment of the present invention is analogously also operable incommunication systems operable pursuant to other operating standards.The following description of exemplary operation is, therefore, by wayof example not by way of limitation.

The communication system includes network infrastructure, here formed ofmultiple networks. Some of the networks are operable pursuant to awireless local area network operating standard, here the IEEE 802.11(b)operating standard, and others are operable pursuant to a cellularcommunication system operating standard, here a 3GPP operating standard.In the exemplary representation of the figure, four wireless local areanetworks 14 are shown, and two cellular communication system networks 16are shown. Three of the wireless local area networks 14, networks 14-1,14-2, and 14-3, are deployed in manners that encompass a common area,here identified by the cell 18-1-3. And, an additional wireless localarea network 14-N is also shown, here representative of a wireless localarea network that encompasses another area, represented by the cell18-N. The wireless local area networks 14 each include interworkingunits (IWUs) 22 that facilitate interworking between the wireless localarea networks and cellular communication system networks, here thecellular communication system networks 16. The wireless local areanetwork 14-1 is directly connected to the cellular system network 16-1.And, the wireless local area network 14-2 is directly connected to thecellular system network 16-2. The networks 16-1 and 16-2 are connected.And, thereby, the wireless local area network 14-1 is also indirectlyconnected to the cellular system network 16-2. And, also, the wirelesslocal area network 14-2 is indirectly connected to the cellular systemnetwork 16-1.

The mobile node 12 is operable, as noted above, pursuant to theoperating standards by which the wireless local area networks and thecellular system networks are operable. The mobile node includestransceiver circuitry, here represented by a transmit part 26 and areceive part 28. The transceiver circuitry is operable in conventionalmanner, operating pursuant to the protocols set forth in the operatingspecifications, to form communication connections with, and effectuatecommunication of data with selected networks in whose coverage areasthat the mobile node is positioned, by way of a radio air interface.

Positioned as shown in the figure, the mobile node is positioned withinthe coverage areas of the wireless local area networks 14-1, 14-2, and14-3. When the mobile node initiates communications, the mobile nodescans for the availability of the wireless local area networks byscanning channels upon which signals are broadcast by such networks. Themobile node, in the exemplary implementation, includes a WLAN scan list32 that identifies WLANs with which the mobile node is permitted toattempt to communicate. The lists identify, for instance, thefrequencies at which the listed wireless local area networks broadcastcontrol, or other, information. Pursuant to interworking between thenetworks, the mobile node is capable of communicating, by way of awireless local area network, with a cellular system network, viz., acommunication station that is coupled to the communication systemnetwork. The mobile node is permitted communication with a cellularsystem network pursuant, e.g., a service subscription. Pursuant to theservice subscription, a home network is associated with the mobile node,typically a network in whose coverage area that the mobile node is mostregularly positioned. Here, the network that forms the home network ofthe mobile node 12 is the network 16-2, identified as the HPLMN (HomePublic Land Mobile Network) associated with the mobile node. Othercellular system networks, not the home network associated with themobile node, are referred to as visited networks. Here, the network16-1, identified as a VPLMN (Visited Public Land Mobile Network).

As noted previously, interworking between the networks 14 and 16conventionally provides for notification to the mobile node, once incommunication connectivity with a wireless local area network, of thecellular system networks with which the wireless local area networkmaintains associations. When the information is delivered to the mobilenode, a user of the mobile node is able to select with which of thecellular system networks, if any, to effectuate communications. Pursuantto existing proposals and practice, the mobile node is provided with theinformation regarding the associated cellular communication systemnetworks pursuant to association procedures in which the mobile nodeattempts authentication with a selected wireless local area network. Theauthentication attempt fails, and pursuant to the failure of theauthentication, the mobile node is provided with the indications of thecellular communication system networks with which the wireless localarea network is associated. However, when the wireless local areanetwork is in direct connection with the home cellular communicationsystem network associated with the mobile node, the mobile node is notprovided with the associated networks to permit a user of the mobilenode to select with which of the cellular communication system networkswith which to communicate. Existing operation, therefore, limits theability of a user of the mobile node to select with which cellularcommunication system network to communicate when the wireless local areanetwork is directly connected to the home network of the mobile node.

Pursuant to operation of an embodiment of the present invention, amanner is provided by which to provide user selection of the cellularcommunication system network with which to communicate even when thewireless local area network with which the mobile node is associated incommunication connectivity is directly connected to the home cellularcommunication system network of the mobile node. The user of the mobilenode is thereby provided opportunity to select with which of theavailable cellular communication system networks to communicateirrespective of whether the home network of the mobile node is directlyconnected to the wireless local area network with which the mobile nodeis associated in the communication connectivity.

The mobile node further includes apparatus 42 of an embodiment of thepresent invention. The apparatus 42 is formed of functional entities,implementable in any desired manner, including, for instance, algorithmsexecutable by processing circuitry.

The apparatus includes a determiner 44 that operates to determinewhether the wireless local area network with which the mobile node is incommunication connectivity is directly connected to the home cellularcommunication system network associated with the mobile node. And, theapparatus includes an identifier that identifies which, if any, of thewireless local area networks to which the mobile node is in thecommunication connectivity is available with which to communicate withthe mobile node. The identifier is operable, at least responsive todeterminations made by the determiner, here indicated to be provided tothe identifier by way of the line 48.

In the exemplary implementation, the determiner includes a directconnection listing 52 that is formed of entries that identify wirelesslocal area networks, such as by their SSID (Service Set Identifier)values and, associated with each entry, an indication of whether thewireless local area network is directly connected to the home cellularcommunication system network associated with the mobile node. Thelisting is permanently stored at the mobile node, provided thereto,e.g., during initial provisioning of the mobile node. In oneimplementation, the listing is updatable to update the identificationsof direct connections with the entries forming the listing as well as toadd, or to remove, entries from the listing. In another exemplaryimplementation, the listing 52 identifies home WLANs.

The determiner receives indications of the wireless local area networkwith which the mobile node is in communication connectivity, hereindicated on the line 54, and the indications are provided to anaccessor and comparator 56. The indications provided on the line 54 areprovided, for instance, by the receive part of the mobile node basedupon detection of information broadcast by the wireless local areanetworks listed on the WLAN scan list 32.

The accessor and comparator 56 accesses the listing 52 and comparesvalues stored thereat with the indications provided on the line 54.Responsive to the comparison, a determination is made as to whether theindication delivered on the line 54 corresponds to an entry on thelisting 52 that identifies that the network identified in the entry isdirectly connected to the home network associated with the mobile node.

Results of the comparison are provided on the line 48 to the identifierthat, in the exemplary implementation, includes an authenticationmessage generator 62. The identifier also includes memory elements thatstore values of root network address identifiers (RNAIs). The rootnetwork address identifier stored at the memory element 64 is of a valuethat correctly identifies the home cellular communication system networkassociated with the mobile node. And, the value stored at the memoryelement 66 is of a different value, i.e., a value that incorrectly, orerroneously, identifies the home network. In other words, the differentvalue is an alternative value.

In an alternate implementation, the different value of the networkaddress identifier is randomly generated and the memory element 66 issubstituted with a random value generator.

When the indications provided on the line 48 identify that the WLAN withwhich the mobile node is in communication connectivity does not have adirect connection to the home network associated with the mobile node,the root NAI associated with the home network, stored at the memoryelement 64 is retrieved, and used by the authentication messagegenerator pursuant to authentication procedures. If, however, thedeterminer determines that the WLAN is directly connected to the homenetwork associated with the mobile node, the value of the networkaddress identifier is retrieved from the memory element 66. And, theauthentication message generator uses this value pursuant toauthentication procedures. Authentication fails when the correct networkaddress identifier is used but the WLAN is not directly connected to thehome network of the mobile node. And, when the WLAN is directlyconnected to the home network, the erroneous network address identifiercauses the authentication to fail. In another implementation, thealternative value, stored at the memory element 66 is always utilizedirrespective of whether the WLAN is directly connected with the homenetwork of the mobile node. Here, also, authentication fails. And,determinations made by the determiner are obviated. Responsive to failedauthentication, the WLAN sends a message to the mobile node thatincludes identification of the cellular communication system networkswith which the WLAN maintains an association. And a user of the mobilenode is able to select from the returned identifications with which ofthe cellular communication system networks that the mobile node shallsubsequently communicate.

In an alternate implementation, a list is maintained at the mobile nodeof known WLANs and their respective associations of PLMNs. When a WLANnoted on the list is located, the authentication procedure that is usedto obtain information regarding the cellular system networks associatedwith the WLAN is not performed, and HPLMN information stored at the listis provided to the user of the mobile node. And, authenticationprocedures using an other NAI is not required to obtain the informationregarding the cellular system networks associated with the WLAN.

FIG. 2 illustrates a representation of the direct connection listing 52that forms part of the apparatus 42 embodied at the mobile node 12(shown in FIG. 1). The listing is exemplary and is here shown to beformed of a plurality of entries 72. With respect to the exemplarycommunication system shown in FIG. 1, four entries, associated with thewireless local area networks 1, 2, 3, and N, form the listing. Eachentry is identified in a first column 76 by a service set identifier(SSID) that identifies each of the wireless local area networks. And, anindication is noted in the column 78 indexed together with the serviceset identifier of the WLAN with which it is associated. Here, the SSIDof the second WLAN 14-2 is directly connected to the home networkassociated with the mobile node. And, the column 78 includes anindication of the direct connection.

FIG. 2B illustrates a listing 52 that is embodied at the mobile node 12pursuant to a further embodiment of the present invention. Here, theentries include an entry 72 identified as WLAN 2, viz., the WLAN 14-2shown in FIG. 1. Here, the inclusion of the WLAN 2 in the listingidentifies the WLAN to have a direct connection with the HPLMN of themobile node.

FIG. 3 illustrates a message sequence diagram representative ofexemplary operation of the communication system 10 shown in FIG. 1.Here, the wireless local area networks 14-1, 14-2, and 14-3 broadcastsignals that are detected by the mobile node. The signals are indicatedin the figures by the segments 82-1, 82-2, and 82-3. The mobile nodeaccesses its WLAN scan list 32 (shown in FIG. 1) to determine to whichchannels to tune. And, by tuning to the identified channels, the mobilenode detects, indicated by the block 86, the transmitted signals.

The mobile node accesses the direct connection listing (shown in FIG.1). Here, accessing and comparing is performed, as indicated by theblock 88. Responsive to the comparisons, determinations are made as towhether the wireless local area network with which the mobile node is incommunication connectivity, here selected to be the wireless local areanetwork 14-2, an authentication message is generated and sent thereto,indicated by the segment 92. Because the network 14-2 is directlyconnected to the network 16-2, here the home network associated with themobile node, the authentication fails. An authentication failureresponse 94 is provided to the mobile node together with indications ofthe networks with which the network 14-2 maintains associations. Oncereceived at the mobile node, the indications of the available networksare displayed, indicated by the block 102, to the user of the mobilenode, and, as indicated by the block 104, the user selects with which ofthe available networks that the mobile node shall communicate.

FIG. 4 illustrates a method, shown generally at 112, representative ofthe method of operation of an embodiment of the present invention. Themethod facilitates communications of a mobile node in a multi-networkcommunication system having a first set of first type networks and asecond set of second type networks. The mobile node is associated with ahome network comprised of a second type network of the second set. Themethod facilitates communications by the mobile node, once the mobilenode is connected in communication connectivity with a first typenetwork of the first set, with a selected network of the second set.

First, and as indicated by the block 114, a determination is made if thenetwork of the first set with which the mobile node is connected in thecommunication connectivity is directly connected with the home network.

Then, as indicated by the block 116, identification is made of which, ifany, of the networks of the second set of networks are available withwhich to communicate with the mobile node.

Thereby, through operation of an embodiment of the present invention, amanner is provided by which to permit a user of a mobile node to selectthe cellular communication system network with which the mobile nodeshall communicate. Selection is possible irrespective of whether thehome network associated with the mobile node is directly connected tothe wireless local area network through which the mobile nodecommunicates.

The previous descriptions are of preferred examples for implementing theinvention, and the scope of the invention should not necessarily belimited by this description. The scope of the present invention isdefined by the following claims.

The invention claimed is:
 1. A method, comprising: sending, from amobile node to a wireless local area network (WLAN), a messagecomprising an alternative network address identifier (NAI), thealternative NAI being different than a root NAI, wherein the root NAIidentifies a home cellular communication system network associated withthe mobile node, and the alternative NAI is selected by the mobile nodeto be unrouteable to the home cellular communication system network; andreceiving, from the WLAN and in response to the message comprising thealternative NAI, a list that identifies a public land mobile network(PLMN) accessible via the WLAN.
 2. The method of claim 1, furthercomprising providing an indication, at the mobile node, of an accessiblePLMN.
 3. The method of claim 1, further comprising generating themessage comprising the alternative NAI.
 4. The method of claim 1,wherein the WLAN is an interworking-WLAN (I-WLAN).
 5. The method ofclaim 1, wherein the home cellular communication system network is ahome PLMN.
 6. The method of claim 1, further comprising selecting a PLMNfrom the list.
 7. The method of claim 6, further comprisingcommunicating with the selected PLMN.
 8. A mobile node, comprising: amemory; and at least one hardware processor communicatively coupled withthe memory and configured to: send, from the mobile node to a wirelesslocal area network (WLAN), a message comprising an alternative networkaddress identifier (NAI), the alternative NAI being different than aroot NAI, wherein the root NAI identifies a home cellular communicationsystem network associated with the mobile node, and the alternative NAIis selected by the mobile node to be unrouteable to the home cellularcommunication system network; and receive, from the WLAN and in responseto the message comprising the alternative NAI, a list that identifies apublic land mobile network (PLMN) accessible via the WLAN.
 9. The mobilenode of claim 8, wherein the at least one hardware processor is furtherconfigured to provide an indication, at the mobile node, of anaccessible PLMN.
 10. The mobile node of claim 8, wherein the at leastone hardware processor is further configured to generate the messagecomprising the alternative NAI.
 11. The mobile node of claim 8, whereinthe WLAN is an interworking-WLAN (I-WLAN).
 12. The mobile node of claim8, wherein the home cellular communication system network is a homePLMN.
 13. The mobile node of claim 8, wherein the at least one hardwareprocessor is further configured to select a PLMN from the list.
 14. Themobile node of claim 13, wherein the at least one hardware processor isfurther configured to communicate with the selected PLMN.
 15. Anon-transitory computer-readable medium containing instructions which,when executed, cause a computing device to perform operationscomprising: sending, from a mobile node to a wireless local area network(WLAN), a message comprising an alternative network address identifier(NAI), the alternative NAI being different than a root NAI, wherein theroot NAI identifies a home cellular communication system networkassociated with the mobile node, and the alternative NAI is selected bythe mobile node to be unrouteable to the home cellular communicationsystem network; and receiving, from the WLAN and in response to themessage comprising the alternative NAI, a list that identifies a publicland mobile network (PLMN) accessible via the WLAN.
 16. Thenon-transitory computer-readable medium of claim 15, the operationsfurther comprising providing an indication, at the mobile node, of anaccessible PLMN.
 17. The non-transitory computer-readable medium ofclaim 15, the operations further comprising generating the messagecomprising the alternative NAI.
 18. The non-transitory computer-readablemedium of claim 15, wherein the WLAN is an interworking-WLAN (I-WLAN).19. The non-transitory computer-readable medium of claim 15, wherein thehome cellular communication system network is a home PLMN.
 20. Thenon-transitory computer-readable medium of claim 15, the operationsfurther comprising selecting a PLMN from the list.